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Cognitive Neuroscience Lecture 2: Neuroanatomy
Neurons—basic connectivity - Information processing/signaling unit of the brain, basic element of computation Folded makes it closer together = faster connections Blood vessels bring nutrients Noninvasive neuroimaging measures oxygen levels in the brain Grey matter: mostly cell bodies White matter: mostly axons & fibres Ventricles: right, left, 3rd, 4th - Brain has no skeleton, so fluid protects it from shock & pressure (offsets) - Contains CSF Three stages of computation: - 1. Receive signals from other cells (“input stage”): o Many signals come in at dendrites - 2. Process those inputs (“processing/evaluation stage”) o Signals summate, adding and canceling, possibly reaching critical threshold within cell body to send an output - 3. Transmit signals to other cells (“output stage”) o If the input is strong enough (exceeds threshold), then the neuron passes the signal along via its axon Synapse—where the axon of one neuron connects to the dendrite of another neuron Release of neurotransmitter at the synapse Pass signal to post-synaptic neuron: - Excitatory signals (EPSP)—increase the probability that the post-synaptic neuron will fire - Inhibitory signals (IPSP)—decrease the probability that the post synaptic neuron will fire Nervous system is a “Chain of Neurons” Sensory Neurons (vision, touch, audition, taste, olfaction)à Interneurons à motor neurons (eye/body mvt) Brain hierarchy: - Neurons (basic element of computation) - Brain structures and areas (collections of neurons) 3 major divisions of the brain: - Cerebral cortex—outer areas - Limbic system—inner structures - Brain stem & cerebellum—deep structures Orientations - Dorsal (superior) ßà Ventral (inferior) - Rostral (anterior) ßà Caudal (posterior) o Spinal cord: closer to head = rostral, closer to tail = caudal - Lateral ßMedialàLateral Cross Sections - Transverse/horizontal—useful for comparing anterior/posterior & right/left - Sagittal—useful for comparing anterior/posterior & inferior/superior - Coronal—useful for comparing inferior/superior & left/right Dissection shows that it’s not as easy to tell irl Lobes - Frontal—high level functions o Reasoning, planning, override and control of social responses, control parts of speech, motor control, emotions, problem solving, executive control - Parietal—body/world interface o Somatosensation, integrating sensory info across senses, spatial processing, attention, number perception - Temporal—perception/memory interface o Auditory sensation/perception, auditory recognition, visual recognition, long term memory, speech production - Occipital lobe—Visual processing Major Folds (Sulci) - Sylvian fissure (lateral sulcus) - Central sulcus - Supramarginal - angular - Parieto-occipital sulcus - Calcarine fissure Gyri - Frontal (superior, middle, inferior), temporal 3 (superior, middle, inferior), central 2 - lateral occipital gyri - cingulate gyrus - cuneate gyrus Subareas within lobes: 52 Brodmann areas - Anatomically subdividing regions of the cortex - Based on cell architectonics: cell microanatomy - Brodmann areas based on similarity/difference of cell architecture - 52 regions Subareas within the lobes: functionally subdividing regions of the cortex - Picture with PFC, orbitofrontal cortex, DLPFC, VLPFC, Frontal cortex, motor, somatosensory, A1, V1 - E.g. subdividing frontal into prefrontal and motor - E.g. sub region of parietal is somatosensory cortex Basic Organizing principle of the cortex: topographical mapping Sensory/Motor cortex has MAPS - Occipital lobe: V1 = a map of visual world in occipital cortex o primary visual cortex, Brodmann’s area 17, area 17, V1 all refer to the same-ish place o retinotopic mapping in humans with fMRI: position map o polar angle map o eccentricity map - Temporal: A1 = a map of sound in auditory cortex o near Sylvian/lateral fissure: A1 (primary auditory cortex) o Tonotopic map: frequency map o Cortical tonotopy: tone frequency MAP in A1 - Parietal: S1 = a map of the body in somatosensory cortex o Electrical stim of motor & somatosensory o Shows map; homunculus § Disproportionate amount for hands & face - Frontal: M1 = another map of the body in motor cortex o Electrical stim shows map o Another homunculus: also disproportionate amt for hands because detailed mvts - Do other areas have maps? Maybe Limbic System: inner structures - Cingulate gyrus o cognitive control o error detection o conflict monitoring - Thalamus o relay station for all of the senses o regulation of sleep and arousal - Hippocampus o Long term memory o Spatial navigation - Amygdala o Emotion processing o Memory for emotive stimuli - Picture of mid sagittal view of these and corpus callosum Brain stem & cerebellum: deep structures - Cerebellum o Most of brain’s neurons are here o Integrates sensory and motor information o Maintain balance of posture, walking, coordinate and time movements o Coordinate muscle movements, motor control o Also involved in some aspects of higher cognitive function; not sure what exactly - Brain stem o Superior colliculus: visual processing o Inferior colliculus: auditory processing o Colliculi are for when an object comes flying at you, you want to get out of the way o Medulla: § Relay signals between brain & spinal cord § Controls autonomic functions (heart/blood pressure/respiration) o Pons: § Relays sensory information between brain & cerebellum § Controls arousal § Important for sleep - Left and right hemispheres connected by corpus callosum